<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            margin:100px;
            width: 300px;
            height: 200px;
            background: lavender;
            background: linear-gradient(to left bottom,transparent 50% ,rgba(153, 140, 140, 0.4) 0)no-repeat 100% 0/2em 2em,
            linear-gradient(-135deg,transparent 1.5em,lavender 0);
        }
        .note {
            margin:100px;
            width: 300px;
            height: 200px;
            position: relative;
            background: #58a; /* 回退样式 */
            background:
            linear-gradient(-150deg,
            transparent 1.5em, #58a 0);
            border-radius: .5em;
        }
        .note::before {
            content: '';
            position: absolute;
            top: 0; right: 0;
            background: linear-gradient(to left bottom,
            transparent 50%, rgba(0,0,0,.2) 0, rgba(0,0,0,.4))
            100% 0 no-repeat;
            width: 1.73em;
            height: 3em;
            transform: translateY(-1.3em) rotate(-30deg);
            transform-origin: bottom right;
            border-bottom-left-radius: inherit;
            box-shadow: -.2em .2em .3em -.1em rgba(0,0,0,.15);
        }
    </style>
</head>
<body>
    <div class="box"></div>
    <div class="note"></div>
</body>
</html>